ᐅ Downspout outside the upper floor exterior wall but within the corner of the ground floor – sound insulation

Hello everyone,

I have a question regarding the design of a detached house (pagoda-style) with a recessed upper floor (set back by 85 cm (33 inches) on each side).

The bathroom waste pipe on the upper floor was planned to be located in the corner wall of the kitchen on the ground floor. Because the upper floor is recessed, this waste pipe will be situated under the first (intermediate) roof, meaning outside the actual exterior wall. This should cause a significant amount of sound transmission from outside, since a roof does not effectively reduce noise, right?

For the double-wall construction, calcium silicate blocks were specifically chosen for the interior layer to improve sound insulation. With this opening in the exposed area (just under the intermediate roof) where the waste pipe passes through, the sound insulation is basically compromised, isn’t it? Is there any way to fix this situation? The shell construction is already at the stage where the floor slab has been poured...

View of the ground floor (left) and upper floor (right):

House cross-section:

Apart from the appearance, you could run the downpipe through the intermediate ceiling space and then down the exterior wall of the ground floor. Or you could discuss with your architect whether it’s allowed to drain through the intermediate ceiling space. (That might no longer comply with current regulations, but it could work with the right design.) In any case, routing the pipe inside like that doesn’t seem very smart to me, even disregarding soundproofing.

Routing the downpipe for wastewater outside is not possible due to frost protection, I was told. Do you mean "watering over the attic space" via the gutter? I have two drain covers, so rainwater and sewage have to be kept separate.

Sorry, my mistake—I was mentally thinking of a "downpipe" related to rain.

Well, running the pipe from the bathroom (toilet?) right next to the dining table isn’t really elegant. We had a rather specific plan for that once, but the general consensus was to avoid it. However, I have personally lived in a house where the soil pipe was routed through the corner of the living room, and it actually worked out. In that case, it was insulated two or three times over to minimize or almost completely prevent noise from entering the living room.

Oh, I see. In my case, there is the specific situation that the hole in the concrete ceiling for the pipe from the bathroom is now located outside the main building envelope, in the roof void. I assume that even with double or triple insulation, more noise would likely enter there?

No, why? First of all, it is still located under the mezzanine ceiling, and secondly, it will be fully enclosed anyway. The important thing is to use enough insulation and perhaps apply double-layered sheathing. However, the best insulation cannot replace good planning.